I would strongly recommend you NOT remove the center brace. This piece of plastic is there to keep the glass panels of the tank from bowing when it's filled with water. If you fill the tank without the brace, you run the risk of the panels bowing too much and cracking.
If you want to take it out I would repalce it with a glass pannel. First put the glass pannel in by siliconing it to the front and back walls. After a couple of days (3-4) cut out the plastic strip. I would not cut it out and leave it that way. Many tanks come with glass pannels siliconed in insted of the plastic strip so it does work.
I have known a few people who have done this and regretted it - especially on bowfronts. Try wazzels suggestion but I would do it before the tank is filled with water personally.
A quasi-eurobraced 46 bowfront would be an awesome tank since you could just about light it with one strong halide.